Solid supported heterogeneous Ziegler Natta catalyst is obtained by contacting a solid support consisting of magnesium halide or a compound which on reaction gives magnesium halide with titanium compound having at least one titanium halogen bond, in presence/absence of electron donating compound.
U.S. Pat. No. 6,841,633 describes the use of less expensive starting material, hydrated magnesium chloride with in-situ generated internal donor. The use of ester is avoided to minimize the generation of byproducts making the catalyst very efficient. U.S. Pat. No. 7,265,074 of the present applicants, teaches a single step process for olefin catalyst synthesis through microwave technique.
Morphology retention is an important criterion for olefin polymerization catalyst in terms of polymerization plant operability and throughput. PCT/IN2008/000555 describes a novel magnesium alkoxide precursor with improved mechanical strength. The claimed precursor retains its shape and size throughout the catalyst and polymerization processes.
The above-mentioned prior art processes suffer from several drawbacks. In all these processes, the process of catalyst synthesis goes through a series of reaction/washing stages. As the number of stages increases, the tendency of particle breakage due to mechanical attrition increases. U.S. Pat. No. 6,770,718 B2 describes a single step reaction process in which solvent is taken in the reactor and cooled: Solid support is charged at lower temperature and donor at 40° C. Pure TiCl4 addition is started during the heating or on reaching the reaction temperature. Simultaneously, liquid is taken out by filtration so as to keep the total volume in the reactor constant. After certain period, the composition of the incoming stream is also changed from pure TiCl4 to 1:1 ratio of TiCl4 and toluene or TiCl4 and ethylbenzene. At the end of the reaction, slurry in the reactor is allowed to settle and supernatant liquid is siphoned off. The resultant solid is subjected to six batch washings. The overall process is batch type and is therefore not commercially advantageous, particularly since the volume of the reactor and total time cycle of batch is not reduced.
US Patent 2008/0194781 A1 describes a process where the catalyst is prepared in three stages. In the first stage, MgCl2.EtOH adduct is treated with triethyl aluminium (TEAL) at lower temperature (0° C.) in continuous manner, where liquid is continuously charged from top and withdrawn from the bottom through a filter while maintaining constant slurry concentration in the reactor. The second stage is treatment of solids with TiCl4, and finally the catalyst is washed in a continuous manner as stated above. In this patent, an additional step of treatment with TEAL at 0° C. is required, making the process very expensive and hazardous. The process also does not specify any method of control over catalyst particle size distribution and fines content. Precursors of different particle size are required to produce catalysts of different particle size.